The goals of this research are to identify patient and organizational characteristics associated with inadequate enrollment of medically eligible subjects in clinical trials. We propose methodology for the development of interview protocols. Qualitative research techniques, including key informants surveys and focus groups, will be used in the preliminary stages of instrument development. Piloting of the protocols will be followed by test-retest reliability studies and measures of internal consistency of scales. Two and possibly three cycles of revision and reliability testing are contemplated. Validity of the protocols will be assessed in an additional sample of 60 subjects by examining the performance of multivariate models derived from the final reliability study. Separate protocols will be developed to examine patient characteristics, interpersonal aspects of the recruitment system, and organizational aspects of the recruitment system. The protocol for patient characteristics will be based in behavioral theory by using the Theory of Reasoned Action to guide choice of variables and scales and to provide an analytic framework. This protocol and the protocol to examine interpersonal aspects of the recrutitment system will be administered by CAST nurse coordinators to samples of 200 enrollees and 200 refusers drawn form selected CAST sites. The questionnaire to assess organizational aspects of the recruitment system will be addressed to nurse coordinators and investigators at all CAST sites. The anticipated outcomes of this research are identification of correlates of enrollment, especially potentially modifiable ones; development of forms for the collection of data describing the recruitment process in future clinical trials, including definition of the medically eligibile pool and reasons for nonenrollment; and formulation of methodology to improve enrollment that can be tested in future clinical trials.